The replacement of a natural lens with an artificial intraocular lens implant in the human eye has become a well known procedure to physicians specializing in ophthalmology. In such a procedure, a cornea-scleral incision is made in the eye through which the natural lens is removed and the artificial intraocular lens is inserted. The intraocular lens may be designed to be positioned within either the interior or posterior chamber of the eye.
Intraocular lenses typically include a central lens section, referred to as the optic, for focusing the light onto the retina. One or more supporting structures, called haptics, extend outwardly from the optic to a line and stabilize the optic with respect to the pupil. Typically, the haptics comprise one or more filamentous or wire-like arms or loops which extend radially outwardly from the periphery of the optic. The haptics may be fixed in position within the eye by sutures or by engagement with predetermined eye tissues.
The optic of the intraocular lens may be made of a rigid material such as polymethylmethacrylate (PMMA) or a soft, flexible, semirigid material such hydrogels, silicones and the like. Filamentous haptics, on the other hand, are usually, if not always, made of rigid materials such as polypropylene, PMMA or the like. This is because semirigid materials tend to be too weak to support the optic within the eye.
Soft, flexible optics offer an advantage over rigid optics in that they can be inserted into the eye or through an incision of reduced size. Smaller incisions are desired to minimize trauma to the eye. For example, Mazzoco U.S. Pat. No. 4,573,998 describes a method for the intrusion of an intraocular lens through a small incision by deforming, e.g. folding, the intraocular lens. Schacher U.S. Pat. No. 4,373,218 describes an inflatable intraocular lens which can be inserted while in a deflated state through a small incision and then inflated once in position within the eye. Siepser U.S. Pat. No. 4,556,998 describes an intraocular lens made of a hydrogel material which is inserted into the eye in a dehydrated non-swollen state and allowed to swell to its final shape within the eye.
One of the problems in the manufacture of intraocular lens having a soft, flexible optic is in the attachment of the haptic to the optic. Conventional methods of haptic attachment such as heat staking do not provide a strong enough bond between the material of the optic and the material of haptic.
Kaplan et al. U.S. Pat. No. 4,668,446 discloses a method for attaching a rigid haptic to a nonrigid or semirigid optic. In this method, a peripheral bore is formed in the optic. The optic is then swollen in an organic fluid to enlarge the bore. A haptic having an enlarged end is then inserted into the bore and the organic fluid is then removed from the optic. This reduces the size of the bore which contracts around the enlarged section securing the haptic to the optic.